Solar energy receiver

ABSTRACT

Solar receiver having a receiver funnel, a solar absorber, and an absorber rotation drive mechanism. The receiver funnel has a funnel entrance and a funnel exit. The solar absorber may have a spherical shape and has an absorber rotation axis. The solar absorber is rotatably positioned in the funnel exit. The solar absorber has an internal absorber fluid chamber, an absorber fluid intake and an absorber fluid outlet. The absorber rotation drive mechanism provides for rotating the solar absorber about the absorber rotation axis.

FIELD OF THE INVENTION

This invention is in the field of devices for collecting solar energyand particular in the field of devices for receiving and absorbingconcentrated solar energy.

BACKGROUND OF THE INVENTION

Incident solar radiation may be focused for solar energy collectionpurposes by mirrors, conventional lenses or Fresnel lenses in variousways known in the art. These collectors all require a device providingfor the reception and absorption of the focused incident solarradiation. Solar collectors utilizing energy transfer to a fluid mediumthat in turn is used to supply energy to a turbine, require a deviceproviding for the efficient reception and absorption of the focusedincident solar radiation and for the efficient transfer of that energyto the liquid medium.

Solar collectors which utilize Fresnel lenses, such as the solarcollectors disclosed in U.S. patent application Ser. No. 10/621,933,Publication No. 20050011513, by the present inventor, regardless of theprecision with which the Fresnel lens components are manufactured,experience some unavoidable scatter in attempting to focus incidentsolar radiation. Scatter is also induced by manufacturing irregularitiesand installation errors for collectors using mirrors and conventionallenses. The result is that, regardless of the type of collector used,all of the incident solar radiation will likely not be focused preciselyto a common focal point. Hence, a solar receiver is needed to accept thefocused solar radiation with scatter, further concentrate the focusedradiation with scatter, and ultimately to direct the radiation to asolar absorber where the energy can be absorbed and transferred to afluid medium.

The solar receiver also needs a solar absorber component that willefficiently absorb the concentrated incident solar radiation andefficiently transfer it to the liquid medium, while minimizing radiativeand convective losses.

An objective of the present invention is to provide a solar receiverhaving a receiver funnel to receive, from a solar collector, focusedsolar radiation with scatter and to further concentrate and direct thesolar radiation to a solar absorber for absorption.

A further objective of the present invention is to provide a solarreceiver having a solar absorber element providing for the efficientabsorption of focused and concentrated incident solar radiation, theefficient transfer of the absorbed solar energy to a liquid medium, andthe minimization of radiative and conductive losses.

SUMMARY OF THE INVENTION

Regardless of the type of solar collector, the objective of the primarylens element and the associated structure is to provide for the incidentsolar radiation to be focused so that it may be cost effectively andefficiently absorbed and utilized as an energy source. Ray scatterresulting from imperfect focusing of the incident solar radiation by aprimary lens structure presents a problem for a solar absorber. Unlessthe solar absorber is oversized, some of the focused incident solarradiation will miss the solar absorber.

A preferred embodiment of the present invention has a receiver funnelwith a funnel entrance which provides for the admission of the scatteredsolar radiation. The receiver funnel has a reflective chamber with auniform cone shape or a parabolic cone shape having a funnel reflectivesurface which will redirect the inadequately focused or scattered raysto a solar absorber. The rays which are not directed toward the solarabsorber enter the funnel entrance at various positions and angles ofincidence less than 90° for all or most of the focused incidentradiation, and all or most of the focused incident solar radiation willbe reflected into and thereby trapped by the receiver funnel.

A solar absorber is positioned in the funnel exit but positioned with aclearance from the funnel exit such as to allow for absorber independentmovement. For preferred embodiments, the absorber movement willpreferably be an absorber rotation of the solar absorber about anabsorber rotation axis. For a preferred embodiment, the absorberrotation axis is perpendicular to the funnel axis which is laterallycentered in the receiver funnel. Preferred embodiments of the solarabsorber have a generally spherical shape.

Preferred embodiments of the solar absorber have an external surfacewith a texture, color, and a thermal conductivity such as to maximizethe absorption of the concentrated funnel radiation. Absorbed energy istransmitted by the absorber wall to the absorber transfer surface wherethe absorbed energy is transferred by the absorber wall to absorbertransfer fluid. The absorber transfer fluid is supplied to an absorberfluid chamber by an absorber fluid supply tube having a fluid supplytube discharge, which is also the absorber fluid intake. Preferably,fluid flow in the absorber fluid chamber will be turbulent flowproviding for better mixing and contact between the absorber transferfluid and the absorber transfer surface. This will provide for moreefficient transfer of the absorbed energy into the absorber transferfluid. The solar absorber may also incorporate copper wool or other heattransfer aid attached to the absorber transfer surface and extendinginto the absorber fluid chamber to aid in the rapid and efficienttransfer of heat from the absorber wall into the absorbing transferfluid.

The heated transfer fluid exits the absorber fluid chamber through theabsorber fluid outlet which is firmly structurally attached to theabsorber wall. An absorber rotation drive mechanism, which may consistof an exit pipe sprocket attached to the heated fluid exit pipe, anabsorber rotation chain and a motorized absorber drive with interactswith the absorber drive chain by a drive sprocket. A variable speeddrive, gear box, or other speed control mechanism may be used to controlthe speed of absorber rotation of the solar absorber.

A mechanical seal with a fluid seal between the rotating fluid exit pipeand the fixed absorber fluid discharge pipe provides for the heatedtransfer fluid to flow from the rotating fluid exit pipe into the fixedabsorber fluid discharge pipe. The absorber fluid discharge pipeconducts the heated transfer fluid to the a heat transfer device, steamturbine, or other energy out take system.

The temperature and the flow rate of the heated transfer fluid may bemeasured and transmitted to an absorber drive controller. The fluidtemperature signal and the fluid flow rate signal may be used by todetermine the rate of the absorber rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-section of a preferred embodiment of a solarreceiver of the present invention with a uniformly decreasing chamberdiameter.

FIG. 2 is a top plan view of the preferred embodiment of the solarreceiver of the present invention shown in FIG. 1.

FIG. 3 is a vertical cross-section of a preferred embodiment of a solarreceiver of the present invention with a parabolically decreasingchamber diameter.

FIG. 4 is a vertical cross-section of a preferred embodiment of a solarabsorber and an absorber rotation mechanism of a solar receiver of thepresent invention.

FIG. 5 is a cross-section detail of an optional heat transfer aid of apreferred embodiment of a solar absorber of a solar receiver of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Regardless of the type of solar collector, the objective of the primarylens element and the associated structure is to provide for the incidentsolar radiation to be focused so that it may be cost effectively andefficiently absorbed. Referring first to FIG. 1, generally focusedincident solar radiation 1 converging upon a focal point 3 is shown. Rayscatter 5 resulting from imperfect focusing of the incident solarradiation by a primary lens structure presents a problem for a solarabsorber. Unless the solar absorber is oversized, some of the focusedincident solar radiation will miss the solar absorber.

For the embodiment of the present invention shown in FIG. 1, a receiverfunnel 7 having a funnel entrance 9 provides for the admission of thescattered solar radiation 11. The embodiment of the receiver funnel 7 ofthe solar receiver 10 shown in FIG. 1 has a reflective chamber 13 with acircular chamber cross section 15 having a chamber diameter 17 as shownin FIG. 2 which decreases uniformly from the funnel entrance 9 to thefunnel exit 21. The receiver funnel 7 has a reflective surface 23. Otherembodiments of the receiver funnel may have a parabolic reflectivesurface 23 as shown on FIG. 3. Receiver funnel 7 embodiments other thanthe uniform cone shape 24 of FIG. 1 and the parabolic cone shape 26 ofFIG. 3 having a funnel reflective surface 23 which will redirect theout-of-focus rays 28, which will be known to persons of ordinary skillin the art in view of the disclosures made in this specification and thedrawings, may also be used.

The funnel reflective surface 23 may be polished, coated or otherwisemirrorized to provide for high reflectivity and associated minimalabsorption by the reflective chamber walls 29. A structure of thereceiver funnel 7 preferred by the inventor is an aluminum cone with ahighly polished funnel reflective surface 23.

The inadequately focused, scattered rays 33 which are not directedtoward the solar absorber 47, enter the funnel entrance 9 at variouspositions and angles of incidence and strike the chamber reflectivesurface 23 at a first reflective point 37 with respective firstreflective angles 39. Because the first reflective angle 39 will be lessthan 90° for all or most of the focused incident radiation 1 from thesolar collector, all or most of the generally focused incident solarradiation 1 will be reflected into and thereby trapped by the receiverfunnel 7. The shape of the receiver funnel 7, the position of the firstreflective point 37, and the magnitude of the first reflective angle 39,for each incident scattered ray 33 will determine the number ofreflections that the ray will experience before striking the solarabsorber 47.

As shown for the embodiments of the solar receiver 10 in FIG. 1 and FIG.3, the solar absorber 47 may be positioned at the funnel exit 21 andimmediately adjacent to the funnel exit perimeter 45, and may beseparated from the funnel exit perimeter 45 by an absorber clearance 49which allows for absorber independent movement 51 of the solar absorberwithout contact with the funnel exit perimeter 45. For the embodiment ofthe solar absorber 47 shown in FIGS. 1-4, the absorber movement 51 willpreferably be an absorber rotation 53 of the solar absorber 47 about anabsorber rotation axis 55. For the embodiment shown, the absorberrotation axis 55 is perpendicular to the funnel axis 56 which islaterally centered in the receiver funnel 7. For the embodiment of thesolar absorber shown in FIGS. 1-4, the solar absorber 47 has a generallyspherical shape 57 and the absorber diameter 59 and the absorberclearance 49 are such that regardless of the final reflective angle 61of a scattered ray 33, all or most of the scattered rays 33 will strikethe absorber external surface 67 as shown in FIG. 4. For the purposes ofthis specification and the claims, the term “spherical” shall be definedto mean spherical or approximately spherical. For preferred embodimentsof the solar absorber 47, the absorber external surface 67 will have atexture, color, and a thermal conductivity such as to maximize theabsorption of the concentrated funnel radiation 65. Although therotation angle 58 between the absorber rotation axis 55 and the funnelaxis 56 may vary, the optimum rotation angle 58 for distributing theincident concentrated radiation and the resultant heat on the absorberexternal surface 67 may be approximately ninety degrees for mostpreferred embodiments.

Referring now to FIG. 4, absorbed energy 69 is transmitted by theabsorber wall 71 to the absorber transfer surface 73 where the absorbedenergy 69 is transferred by the absorber wall to absorber transfer fluid75. For the embodiment of the solar absorber shown in FIG. 4, theabsorber transfer fluid may be supplied to an absorber fluid chamber 77by an absorber fluid supply tube 79 having a fluid supply tube discharge81, which is also the absorber fluid intake for the embodiment shown,positioned a discharge clearance 83 from an absorber fluid dischargecontact zone 87. Some of the absorber transfer fluid 75 discharged fromthe fluid supply tube 79 may initially contact the absorber transfersurface 73 at the discharge contact zone 87 and experience fluiddispersal 88 in the absorber fluid chamber 77. For a preferredembodiment the fluid flow 90 in the absorber fluid chamber 77 will be aturbulent flow providing for better mixing and contact between theabsorber transfer fluid 75 and the absorber transfer surface 73. Thiswill provide for more efficient transfer of the absorbed energy 69 intothe absorber transfer fluid 75. The heated transfer fluid 89 exits theabsorber fluid chamber 77 through the absorber fluid outlet 92, whichfor the embodiment shown in FIG. 4, is heated fluid exit pipe 91 whichis firmly structurally attached to the absorber wall 71. For thepreferred embodiment shown in FIG. 4, an absorber rotation drivemechanism 93, which may consist of an exit pipe sprocket 95 attached tothe heated fluid exit pipe 91, an absorber rotation chain 97 and amotorized absorber drive 99 which interacts with the absorber drivechain 97 by a drive sprocket 101. A variable speed drive, gear box, orother speed control mechanism 100 may be used to control the rate ofabsorber rotation 53 of the solar absorber 47. Other drive mechanismsand rotation speed control mechanisms for imparting and controlling exitpipe rotation 106 for the fluid exit pipe 91, and thus impartingabsorber rotation 53 to the solar absorber 47 will be obvious to personsof ordinary skill in the art in view of the disclosures made in thisspecification and the drawings.

For the embodiment shown in FIG. 4, a mechanical seal 102 with a fluidseal 104 between the rotating fluid exit pipe 91 and the fixed absorberfluid discharge pipe 105 provides for the heated transfer fluid 89 toflow from the rotating fluid exit pipe 91 into the fixed absorber fluiddischarge pipe 105. The absorber fluid discharge pipe 105 may conductthe heated transfer fluid 89 to the a heat transfer device, steamturbine, or other energy out take system.

Referring to FIG. 5, a preferred embodiment of the solar absorber 47 mayincorporate copper wool 107 or other heat transfer aid attached to theabsorber transfer surface 73 and extending into the absorber fluidchamber 77. This may substantially aid in the rapid and efficienttransfer of heat from the absorber transfer surface 73 into the absorbertransfer fluid 75.

Referring again to FIG. 4, a preferred embodiment of the solar receiver10 may also incorporate an external infrared barrier element 111positioned to enclose the non-absorbing surface of the solar absorber 47which has been rotated out of the reflective chamber 13 to reduce theamount of infrared radiation losses from the solar absorber 47 byreflecting 112 the emitted infrared 110 back to the absorber wall 71.The infrared barrier element 111 may also be sealed against the funnelexit perimeter 45 and used to reduce convective losses of heat emanatingfrom the solar absorber 47.

Referring again to FIG. 1, a preferred embodiment of the receiver funnel7 may also incorporate an internal infrared reflector 113 positioned inthe reflective chamber 13. This may be used to reduce the amount ofinfrared radiation losses from the solar absorber 47 by reflecting 112the emitted infrared 110 back to the absorber wall 71. The infraredbarrier element 113 may also be sealed against the funnel reflectivesurface 23 and used to reduce convective losses of heat emanating fromthe solar absorber 47.

Although the solar receiver of the present invention shown in FIGS. 1-5is a preferred embodiment having a receiver funnel 7 with a circularfunnel exit 21 and a spherical solar absorber 47 having an absorberrotation 53 about an absorber rotation axis 55 which is approximatelyperpendicular to the funnel axis 56 laterally centered in the receiverfunnel 7, other embodiments may incorporate a solar absorber of anon-spherical shape which may have an absorber rotation axis which isnot necessarily perpendicular to the funnel axis, and the funnel exitmay be non-circular and configured to provide for the solar absorber tobe movably positioned proximal to the funnel exit and the funnel exitperimeter. The absorber movement drive mechanism provides for moving thesolar absorber with respect to the funnel exit and the funnel exitperimeter.

Referring again to FIG. 4, the temperature of the heated transfer fluid89 may be measured by a transfer fluid temperature sensor 121 which maytransmit a fluid temperature signal 123 to an absorber drive controller119. The flow rate of the heated transfer fluid 89 may also be measuredby a transfer fluid flow rate sensor 125 which may transmit a fluid flowrate signal 127 to the absorber drive controller 119. The fluidtemperature signal 123 and the fluid flow rate signal 127 may be used bythe absorber drive controller 119 to generate and transmit an absorberdrive control signal 117 to the motorized absorber drive 99 or a speedcontrol signal 115 to the speed control mechanism 100, or both.Accordingly, the fluid temperature signal 123 and the fluid flow ratesignal 127 may be used in the determination of the rate of the absorberrotation 53.

Other embodiments and other variations and modifications of theembodiments described above will be obvious to a person skilled in theart, in view of the disclosures of the specification and the drawings.Therefore, the foregoing is intended to be merely illustrative of theinvention and the invention is limited only by the following claims andthe doctrine of equivalents.

What is claimed is:
 1. Solar receiver for receiving, from a solarcollector, focused solar radiation with scatter and to furtherconcentrate and direct the solar radiation with scatter to a solarabsorber for absorption, the solar receiver comprising: a receiverfunnel having a funnel entrance and a funnel exit with a funnelperimeter; a solar absorber movably positioned proximal to the funnelexit and the funnel exit perimeter, the solar absorber having aninternal absorber fluid chamber, an absorber fluid intake and anabsorber fluid outlet; and an absorber movement drive mechanismproviding for moving the solar absorber with respect to the funnel exitand the funnel exit perimeter.
 2. The solar receiver recited in claim 1further comprising an absorber fluid re-circulation system.
 3. The solarreceiver recited in claim 1 wherein the receiver funnel has a funnelentrance and a reflective chamber with a circular chamber cross sectionhaving a chamber diameter which decreases uniformly from the funnelentrance to the funnel exit.
 4. The solar receiver recited in claim 1wherein the receiver funnel has a funnel entrance and a reflectivechamber with a circular chamber cross section having a chamber diameterwhich decreases parabolically from the funnel entrance to the funnelexit.
 5. Solar receiver to receive, from a solar collector, focusedsolar radiation with scatter and to further concentrate and direct thesolar radiation with scatter to a solar absorber for absorption, thesolar receiver comprising: a receiver funnel having a funnel entranceand a funnel exit with a funnel perimeter; a solar absorber having aspherical shape and an absorber rotation axis, the solar absorber beingrotatably positioned in the funnel exit and immediately adjacent to thefunnel exit perimeter, the solar absorber having an internal absorberfluid chamber, an absorber fluid intake and an absorber fluid outlet;and an absorber rotation drive mechanism providing for rotating thesolar absorber about the absorber rotation axis.
 6. The solar receiverrecited in claim 5 further comprising an absorber fluid re-circulationsystem.
 7. The solar receiver recited in claim 5 wherein the receiverfunnel has a funnel entrance and a reflective chamber with a circularchamber cross section having a chamber diameter which decreasesuniformly from the funnel entrance to the funnel exit.
 8. The solarreceiver recited in claim 5 wherein the receiver funnel has a funnelentrance and a reflective chamber with a circular chamber cross sectionhaving a chamber diameter which decreases parabolically from the funnelentrance to the funnel exit.
 9. Method for receiving, from a solarcollector, focused solar radiation with scatter and to furtherconcentrating and directing the solar radiation with scatter to a solarabsorber for absorption, the method comprising: trapping the solarradiation with scatter with a receiver funnel having a funnel entranceand a funnel exit with a funnel perimeter; concentrating the solarradiation with scatter to concentrated solar radiation and directing theconcentrated solar radiation by the receiver funnel to a solar absorber;and absorbing the concentrated solar radiation by the solar absorber,the solar absorber being movably positioned proximal to the funnel exitand the funnel exit perimeter, the solar absorber having an internalabsorber fluid chamber, an absorber fluid intake, an absorber fluidoutlet, and the solar absorber having an absorber movement drivemechanism providing for moving the solar absorber with respect to thefunnel exit and the funnel exit perimeter.
 10. The method recited inclaim 9 further comprising recirculating absorber fluid through thesolar absorber by an absorber fluid re-circulation system.
 11. Themethod recited in claim 9 wherein the receiver funnel has a funnelentrance and a reflective chamber with a circular chamber cross sectionhaving a chamber diameter which decreases uniformly from the funnelentrance to the funnel exit.
 12. The method recited in claim 9 whereinthe receiver funnel has a funnel entrance and a reflective chamber witha circular chamber cross section having a chamber diameter whichdecreases parabolically from the funnel entrance to the funnel exit. 13.Method for receiving, from a solar collector, focused solar radiationwith scatter and to further concentrating and directing the solarradiation with scatter to a solar absorber for absorption, the methodcomprising: trapping the solar radiation with scatter with a receiverfunnel having a funnel entrance and a funnel exit with a funnelperimeter; concentrating the solar radiation with scatter toconcentrated solar radiation and directing the concentrated solarradiation by the receiver funnel to a solar absorber; and absorbing theconcentrated solar radiation by the solar absorber, the solar absorberhaving a spherical shape and an absorber rotation axis, the solarabsorber being rotatably positioned in the funnel exit and immediatelyadjacent to the funnel exit perimeter, the solar absorber having aninternal absorber fluid chamber, an absorber fluid intake, an absorberfluid outlet, and the solar absorber having an absorber movement drivemechanism providing for rotating the solar absorber about the absorberrotation axis.
 14. The method recited in claim 13 further comprisingrecirculating absorber fluid through the solar absorber by an absorberfluid re-circulation system.
 15. The method recited in claim 13 whereinthe receiver funnel has a funnel entrance and a reflective chamber witha circular chamber cross section having a chamber diameter whichdecreases uniformly from the funnel entrance to the funnel exit.
 16. Themethod recited in claim 13 wherein the receiver funnel has a funnelentrance and a reflective chamber with a circular chamber cross sectionhaving a chamber diameter which decreases parabolically from the funnelentrance to the funnel exit.